This project focusses on the changes in striatal dopamine (DA) turnover after unilateral striatal kainic acid lesions. DA turnover will be evaluated by the rate of DA disappearance after tyrosine hydroxylase inhibition. Simultaneously, levels of homovanillic acid and 3,4-dihydroxyphenyl acetic acid will be measured as markers for dopaminergic activity. Particular emphasis will placed on the chronological development of these changes on the homolateral side after 1-48 hours. Preliminary data indicate an increase of striatal DA turnover in response to kainic acid. It will be tried to regulate or modify this increase by intrastriatal or intranigral injections of two dopaminergic drugs, apomorphine and haloperidol. At ten or more days after unilateral kainic acid lesions DA turnover on the contralateral side is decreased as compared to control stiata. The development of this decrease will be studied at eight time points between 4 days and 8 weeks. It is hoped that this time curve can be paralleled by a decrease in spontaneous circling behavior in kainic acid lesioned animals. The information obtained during the course of the proposed project should thus provide a better understanding of striatal mechanisms involving the dopaminergic system. This should prove particularly useful for studying unilateral disorders of the basal ganglia.